Rotating frame animal traps of the type described herein generally have frames of square or rectangular shape as described in U.S. Pat. No. 3,010,245; alternatively, the frames may be partially trapezoidal as described in U.S. Pat. No. 3,760,531. The trap includes at least one actuator, comprising a coil spring having arms terminating in rings which are slidable along and encircle one set of adjacent ends of the frames. The actuator is used to urge the jaws toward a closed position and maintain them in that position. In the aforesaid U.S. Pat. No. 3,010,245, such a rotating frame trap is described wherein the ends which cooperate with the rings are shaped so that in the set position of the trap, outer portions of these ends on each side of central portions lie substantially parallel to one another, while the central portions of these ends near the common axis of the frames form a cross with each other within the rings on the arms of the coil spring. In this version of the trap, the jaw-forming sides of each of the frames lie in a common plane and the outer portions of the ends extend directly to the jaws. A trigger and release mechanism (for example, as described in U.S. Pat. Nos. 2,947,107; 3,762,094; and 3,816,955) maintains the frames in an open position when the trap is set. When the trap is sprung, such mechanism releases the frames so as to permit rapid rotation of the frames through the action of the actuator rings, through an angle of about 90.degree. so that the jaws quickly strike and squeeze an animal in the trap.
This type of trap is widely used because it is based on humane principles. It has been favored by numerous humane trapping groups because it constitutes a substantial improvement over such traps as the leg-hold trap. However, despite the present wide usage of rotating frame traps and their humane effectiveness, there is a constant demand from humane trapping groups to improve the humane efficiency of the trap, i.e. to make the trap more effective so that it kills any desired animal passing through it as quickly as possible. Unless an animal caught in such a trap is killed instantly by the impact of the jaws on its body, the trap may then act as a body-holding trap and consequently death may be extremely slow and painful. It can thus be readily appreciated that if improvements can be made whereby the trap clamping force can be increased, the humane effectiveness of the trap will be improved.
Prior art attempts to increase the clamping force of rotating frame animal traps may be found in U.S. Pat. Nos. 4,117,623 and 4,250,654. In U.S. Pat. No. 4,117,623, the jaw, in the closed trap position, projects out of plane from the frame end members and toward the jaw of the opposing frame member. The juncture between the end members and the projecting jaw-forming side is configured so that the actuator ring encircles and bears against the adjacent frame ends in the closed trap position, thereby permitting a quicker and more humane death for the animal. In U.S. Pat. No. 4,250,654, the frame end members are formed in subsections with particular angular relationships intended to maximize the clamping force between the jaws. While both of these devices are effective for their intended purpose, neither one provides the correct jaw spacing in the closure position combined with maximum utilization of spring force for a given actuator.
The force which a trap develops at a given point in the travel of the actuator rings along the frame ends is dependent upon a number of factors, such as the power of the actuator spring, the diameter and shape of the actuator ring, the distance of the rings from the frame pivot point, and the frame design and geometry. The present invention makes use of a given actuator to maximize its closure force while providing the correct jaw spacing in the closed trap position to more readily kill the trapped animal on closure impact.